The present invention relates to a generator set for a transport refrigeration system. More specifically, the present invention relates to a control system for a multi-speed generator set that changes the speed of the generator set based on a load of the transport refrigeration system.
Existing transport refrigeration systems are used to cool containers, trailers, and other similar transport units. Modern containers may be efficiently stacked for shipment by ship or rail. When containers are shipped by truck, a single container is placed on a trailer chassis. When cargo in the container includes perishable products (e.g., food product, flowers, etc.), the temperature of the container must be controlled to limit loss of the cargo during shipment.
Some existing transport units include a generator set that supplies power to temperature-controlling components of the transport refrigeration system. These generator sets are typically attached directly to the container or trailer, and include an engine or motor to power a generator. During shipment of the transport units, the transport refrigeration systems must operate for extended periods of time (e.g., days, weeks).
Existing generator sets operate at a single, relatively constant speed to produce a constant output frequency and one or more output voltages (e.g., 230/460 VAC, etc.). The speed of these generator sets must be fast enough to provide adequate electrical power to the transport refrigeration system when the transport refrigeration system has a high demand or load. However, these generator sets operate at the same single speed regardless of whether the load on the transport refrigeration system is relatively high or relatively low. During extended periods of time without inspection by transportation workers, these generator sets may experience an out-of-fuel condition caused by operation of the generator set at the same single speed. The out-of-fuel condition causes a loss of power to the transport refrigeration system that may result in a loss of the perishable cargo. This is especially true when ambient temperature conditions are very hot or very cold.